Front-side imager having a reduced dark current on SOI substrate

Abstract

A front-side image sensor may include a substrate in a semiconductor material and an active layer in the semiconductor material. The front side image sensor may also include an array of photodiodes formed in the active layer and an insulating layer between the substrate and the active layer.

The invention claimed is: 
     
       1. A front-side image sensor comprising:
 a silicon-on-insulator (SOI) substrate comprising a semiconductor bulk region and an oxide insulating layer on an upper surface of said semiconductor bulk region; 
 an active layer carried by the SOI substrate; 
 an array of photodiodes in the active layer; and 
 at least one trench isolator extending through said active layer to couple with an upper surface of said oxide insulating layer; 
 said SOI substrate configured to be biased at a voltage lower than a voltage of the active layer during operation. 
 
     
     
       2. The front-side image sensor of  claim 1 , wherein the oxide insulating layer comprises a silicon oxide layer having a thickness in a range to reflect photons in a visible range. 
     
     
       3. The front-side image sensor of  claim 1 , further comprising an intermediate layer between the insulating layer and the active layer, the intermediate layer having a same conductivity type as the active layer and having a higher doping level than the active layer. 
     
     
       4. The front-side image sensor of  claim 1 , further comprising:
 a passivation layer carried by the active layer; 
 an array of colored filters carried by the passivation layer; and 
 an array of collimating lenses carried by the array of colored filters. 
 
     
     
       5. A front-side image sensor comprising:
 a silicon-on-insulator (SOI) substrate comprising a semiconductor bulk region and an oxide insulating layer on an upper surface of said semiconductor bulk region; 
 an active layer carried by the SOI substrate; 
 an array of photodiodes in the active layer; and 
 at least one trench isolator extending completely through said active layer to couple with an upper surface of said oxide insulating layer. 
 
     
     
       6. The front-side image sensor of  claim 5 , wherein the oxide insulating layer comprises a silicon oxide layer having a thickness in a range to reflect photons in a visible range. 
     
     
       7. The front-side image sensor of  claim 5 , further comprising an intermediate layer between the insulating layer and the active layer, the intermediate layer having a same conductivity type as the active layer and having a higher doping level than the active layer. 
     
     
       8. The front-side image sensor of  claim 5 , wherein the SOI substrate is configured to be biased at a voltage lower than a voltage of the active layer during operation. 
     
     
       9. The front-side image sensor of  claim 5 , further comprising:
 a passivation layer carried by the active layer; 
 an array of colored filters carried by the passivation layer; and 
 an array of collimating lenses carried by the array of colored filters. 
 
     
     
       10. A front-side image sensor comprising:
 a silicon-on-insulator (SOI) substrate comprising a semiconductor bulk region and an oxide insulating layer on an upper surface of said semiconductor bulk region; 
 an active layer carried by the SOI substrate; 
 an array of photodiodes in the active layer; and 
 at least one trench isolator extending through said active layer to contact an upper surface of said oxide insulating layer. 
 
     
     
       11. The front-side image sensor of  claim 10 , wherein the oxide insulating layer comprises a silicon oxide layer having a thickness in a range to reflect photons in a visible range. 
     
     
       12. The front-side image sensor of  claim 10 , further comprising an intermediate layer between the insulating layer and the active layer, the intermediate layer having a same conductivity type as the active layer and having a higher doping level than the active layer. 
     
     
       13. The front-side image sensor of  claim 10 , wherein the SOI substrate is configured to be biased at a voltage lower than a voltage of the active layer during operation. 
     
     
       14. The front-side image sensor of  claim 10 , further comprising:
 a passivation layer carried by the active layer; 
 an array of colored filters carried by the passivation layer; and 
 an array of collimating lenses carried by the array of colored filters.